1. Field of the Invention
The present invention relates to a toner that is used to form a toner image by the development of the electrostatic latent image formed by methods such as electrophotographic methods, electrostatic recording methods, and toner jet recording methods.
2. Description of the Related Art
There has been demand in recent years for a reduction in printer and copier power consumption and improvements in toner properties. On the other hand, there has also been demand for problem-free use in a variety of environments. Meeting both of these demands requires the resolution of a trade-off relationship, i.e., suppressing property changes during high-temperature storage while also having the toner soften at lower temperatures. To respond to this problem, investigations have been carried out into toners that incorporate a crystalline resin that exhibits an excellent thermal responsiveness, i.e., an excellent sharp melt property.
Japanese Patent Application Laid-open No. 2006-106727 provides a toner in which lamellar crystals of a crystalline polyester are present in spherical form at the toner surface and in its interior.
With this toner, the heat-resistant storability is maximally maintained through maintenance of the crystallinity of the crystalline polyester in the toner, while the toner readily collapses during fixing due to liquefaction of the crystalline polyester, resulting in an improved low-temperature fixability of the toner. These effects serve to resolve the trade-off relationship cited above. However, in particular during high-speed fixing, the crystalline polyester present in spherical form and the toner binder do not melt uniformly, and not only is a satisfactory low-temperature fixability then not obtained, but during high-speed fixing a phenomenon can occur in which a portion of the toner undergoes melt adhesion to the fixing roller (hot offset phenomenon).
Japanese Patent Application Laid-open No. 2012-255957 provides a toner that has a core/shell structure and that contains a crystalline polyester and a styrene-acrylic resin as binder resins.
With this toner, an improvement in the hot offset phenomenon is pursued by utilizing the elasticity of the styrene-acrylic resin. However, the compatibility between the crystalline polyester and styrene-acrylic resin, which is the toner binder, has not been thoroughly considered. As a result, the toner does not undergo uniform melting during fixing and a satisfactory low-temperature fixability may not be obtained. Japanese Patent Application Laid-open No. Sho 63-27855 and Japanese Patent Application Laid-open No. Sho 62-273574 provide toners that use a block polymer in which a crystalline polyester is bonded to an amorphous polymer that is substantially incompatible.
With these toners, however, when this block polymer is used as the main component, the probability that the crystalline polyester will be present at the toner surface is high and it is quite difficult to cope with speeding up the development system. In addition, with regard to the case in which another resin is made the main component and this block polymer is added, the compatibility between the other polymer and the block polymer has not been thoroughly considered and in some instances it has not been possible to achieve a satisfactory low-temperature fixability.
Thus, while the fixing properties provided by the addition of a crystalline resin have been satisfactorily utilized in these crystalline resin-containing toners, a toner has yet to be introduced that suppresses the adverse effects on the storability and the developing performance.